Agentic Payments Reference Architecture
The reference architecture for verified agentic payments: every component, every interaction, and every verification point. This is the technical foundation for building agent-driven transaction systems.
In This Guide
System Components · Architecture Layers · Verification Pipeline · Online vs. Offline Architecture · Replay Protection Architecture · Integration Points · Implementation Assumptions
Trust Signals & Evidence
Author: AffixIO (Kris & Becca Richens). See What is AffixIO.
Method: The reference architecture is organized around verifiable artifacts and deterministic check pipelines so it works reliably both online and offline (with bounded replay exposure).
Privacy: Stateless verification by design; no PII stored. See Privacy Policy.
Last updated: March 18, 2026
Further reading: trust infrastructure, verified AI agent payments, OWASP API Security.
Architecture Checklist (Build & Integrate)
Before shipping an agentic payments verification system, confirm the architecture covers:
- Clear components — user/policy, agent/credentials + receipt, issuer decision, merchant acceptance, verification layer.
- Deterministic verification pipeline — ordered checks and stable reason codes.
- Online and offline models — define how replay protection works during offline windows.
- Nonce store design — consistent, distributed access for anti-replay and bounded TTL cleanup.
- Key management — secure private keys (HSM/KMS) and safe public key distribution/rotation.
- Integration points — merchant checkout, authorization network, and settlement evidence logging.
- Observability — monitoring for verification success/failure, replay attempts, and latency percentiles.
For implementation assumptions and component options, see the related sections below in this guide.
Reference Architecture Graph
This diagram shows how the major components connect into an end-to-end verified agent payment flow:
For what to verify at each stage, see verified AI agent payments.
Architecture Failure Modes (Integration Gaps)
| Missing or weak component | Resulting verification risk | What to fix |
|---|---|---|
| Nonce store inconsistent across nodes | Replay safety breaks under load | Use a shared nonce store with consistent TTL policy |
| Unclear deterministic check order | Unreliable reason codes and evidence | Define a fixed evaluation pipeline and structured output |
| No offline freshness policy | Offline abuse window becomes undefined | Define bounded freshness windows and reconnect reconciliation |
| Key management not hardened | Signature validation trust becomes weak | Store private keys in HSM/KMS and rotate safely |
| Limited observability | Disputes are harder to investigate | Instrument success/failure rate, replay attempts, and latency percentiles |
System Components
The architecture comprises six core components:
User
Sets policy, issues consent, delegates permissions to agent.
Agent
Holds credentials and consent receipt. Initiates transactions on behalf of user.
Merchant
Receives payment request. Verifies agent identity and consent before accepting.
Verification Layer
Evaluates receipt against transaction context. Returns binary YES/NO with proof.
Policy Engine
Applies issuer rules: risk, compliance, velocity, geographic restrictions.
Issuer
Authorizes transaction. Applies policy, logs proof object, settles payment.
Architecture Layers
Verification Pipeline
The full pipeline runs 13 checks in sequence. If any check fails, the pipeline short-circuits with a NO decision and the failure reason. See verified agent payments for the complete list.
Online vs. Offline Architecture
Online Mode
Full verification with authoritative replay check. Nonce stored in centralized store (Redis, Postgres). Latency: <5ms. Status: ONLINE_VERIFIED.
Offline Mode
Local verification with deferred replay sync. Signature and constraint checks only. Freshness window limits offline drift. Status: VERIFIED_OFFLINE or NEEDS_RECONNECT.
See resilient offline verification for the complete offline model.
Replay Protection Architecture
The nonce store is the critical state component. Options:
- In-memory — Fastest. Single-instance only. Not durable.
- File-based — Persistent. Suitable for development and small deployments.
- Redis — Distributed. Supports clustering. TTL-based automatic cleanup.
- PostgreSQL — Full ACID. Suitable for regulated environments.
All implementations share the same ReplayStore interface. See ACRRV prototype.
Integration Points
The architecture integrates with existing payment infrastructure at three points:
- Merchant checkout — Agent presents receipt alongside payment instrument
- Authorization network — Verification result included in authorization message
- Settlement — Proof object attached to settlement record
Implementation Assumptions
- All participants have access to issuer public keys for signature verification
- NTP time synchronization across all verification nodes
- TLS 1.2+ for all network communication
- Private keys stored in HSM or key management service
- Nonce store is durable and consistent for online verification
Ready to implement?
Explore the reference architecture or request a technical walkthrough.
Frequently Asked Questions
User (consent issuer), Agent (credential holder), Merchant (payment acceptor), Verification Layer (receipt checker), Policy Engine (rule evaluator), and Issuer (authorization authority).
Signature and constraint checks are performed locally. Replay protection uses a local nonce cache with deferred sync on reconnect. A freshness window limits the offline duration.
Redis for distributed deployments, PostgreSQL for regulated environments. In-memory is suitable for development only.